468 / 2018-09-06 08:45:19

Synthesis of renewable polyacids with pinacol and unsaturated carboxylic acids/or aldehydes

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With the increasing of the social concern about energy and environmental problems, the substitution of fossil resources with renewable and CO2 neutral biomass as the feedstock for fuels and chemicals is drawing more and more attention. Lignocellulose is the main component of agricultural and forestry wastes. Compared with fossil feedstock, lignocellulose is richer in oxygenic groups. Therefore, the selective conversion of lignocellulose and its derivates to high value oxygenates has great significance. Polyacids are important monomers for polyester industry. Pinacol is a renewable vic-diol that can be produced by the metal-mediated coupling or electrolytic reduction of acetone from the acetone-butanol-ethanol (ABE) fermentation of lignocellulose. In this work, we developed a series routes for the synthesis of polyacids with pinacol and lignocellulose derived unsaturated carboxylic acids/or aldehydes.
Synthesis of pyromellitic acid with pinacol and diethyl maleate. Pyromellitic acid (PMA) is a monomer for polyimide which is widely used as in the production of engineering plastics, microelectronics, flat panel displays, separation membranes, and aerospace. Diethyl maleate is the esterification product of cellulosic ethanol and maleic anhydride (MA), which can be produced by the oxidation of furfural, 5-hydroxylmethylfurfural (HMF) or levulinic acid (LA) from the hydrolysis/dehydration of hemicellulose or cellulose. In the first part of this work, it was found that PMA can be produced by the one-step selective pinacol dehydration and D-A reaction with diethyl maleate, followed by an integrated one-pot dehydrogenation/hydrolysis cascade, and aerobic oxidation catalyzed by NHPI/Co(OAc)2/Mn(OAc)2 system.
Synthesis of phthalic acid with pinacol and acrolein. Phthalic acid is a widely used plasticizer for PVC products. Acrolein is the dehydration product of glycerol, which is currently oversupplied as a byproduct in the biodiesel production. In the second part of this work, it was found that phthalic acid can be synthesized by the selective dehydration of pinacol to 2,3-dimethylbutadiene, followed by the production of o-xylene by the one-pot D-A cycloaddition and decarbonylation/aromatization reaction of 2,3-dimethylbutadiene with acrolein, and the subsequent oxidization of o-xylene.
Synthesis of trimellitic acid with pinacol and diethyl maleate. Trimellitic acid (TMA) is a widely used plasticizer. Ethyl acrylate is the esterification product of cellulosic ethanol and acrylic acid which can be produced by the dehydration of lactic acid from the catalytic conversion of carbohydrates. In the third part of this work, it was found that TMA can be produced by the one-step selective pinacol dehydration and D-A reaction with ethyl acrylate, followed by an integrated one-pot dehydrogenation/hydrolysis cascade, and aerobic oxidation catalyzed by NHPI/Co(OAc)2/Mn(OAc)2 system. Crotonaldehyde can be prepared by the self-aldol condensation of biomass-derived acetaldehyde. As another option for the production of renewable TMA, it was found that phthalic acid can be synthesized by the selective dehydration of pinacol to 2,3-dimethylbutadiene, followed by the production of 1,2,4-trimethylbenzene by the one-pot D-A cycloaddition and decarbonylation/aromatization reaction of 2,3-dimethylbutadiene with crotonaldehyde, and the subsequent oxidization of 1,2,4-trimethylbenzene.